NDUSTR1AL LIGHTING CODE 


TH 7975 
. F2 W5 
1921 
Copy 1 


FOR 


FACTORIES, MILLS, OFFICES AND 
OTHER WORK PLACES 


THIRD EDITION—REVISED 


ISSUED BY THE 

INDUSTRIAL COMMISSION OF WISCONSIN 



MADISON, WISCONSIN 
Democrat Printing Company, State Printer 

1921 




Industrial Commission of Wisconsin 


GEO. P. HAMRREOHT, Chairman 

FRED M. WILCOX THOMAS F. KONOP 

E. E. WITTE, Secretary .. 

R. McA. KEOWN, Engineer JOHN A. HOEVELER, Electrical Engr. 


INDUSTRIAL LIGHTING CODE 


FOR 


FACTORIES, MILLS, OFFICES AND 
OTHER WORK PLACES 


THIRD EDITION—REVISED 


ISSUED BY THE 

INDUSTRIAL COMMISSION OF WISCONSIN 



MADISON,, WISCONSIN 
Democrat Printing Company, State Printer 
1921 




Industrial Lighting Code Not a Hard¬ 
ship on Employers 

Although most factory managers consider lighting as 
an expense, it should be looked upon as an instrument of 
production. 

A few managers have found from experience, that 
when the lighting is made very good, it advances into a 
class with income producing investments. 

They have learned that three or four times the amount 
of lighting ordinarily used has a remarkably beneficial 
influence on production. 

The increased cost of such “productive lighting” is 
only a fraction of the value of the extra goods produced. 

The reason for this should be easy to understand. The 
production of any skilled workman depends upon his 
speed and accuracy. 

Give him poor light and he is hampered in his work. 
Give him good light and those frequent little delays, so 
inescapable with poor light are eliminated, and he works 
more accurately. 

Moreover, the workman is not particularly conscious of 
his increased efficiency. He works along as usual, but 
because the lighting is right, he just naturally is faster 
and more accurate. 

If this is true, and experience proves it to be true, is 
not “productive lighting” of 'paramount interest to every 
factory manager? 

Of course the state has set certain legal minimum 
standards of lighting for factories, mills and other work 
places, for the protection of the eyesight of the workman 
and to decrease industrial accidents. Therefore every 
industrial manager is compelled to interest himself in 
factory lighting to the extent of meeting at least the 
legal minimum standard in his works. 

However, the legal minimum standards are only a 
fraction of the “productive lighting” standards. 

Therefore any manager who installs “productive light¬ 
ing” in order to gain its benefits of increased produc¬ 
tion, will find that he has automatically taken care of 
the requirements set forth by the Industrial Lighting 
Code. , 

INDUSTRIAL COMMISSION OF WISCONSIN. 



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pig. 2.—The light ceiling adds much to the favorable appearance of the lighted room, increases 
the useful illumination at the work, and reduces brightness contrasts, in this paper box factory. 





















TABLE OF CONTENTS 


Part I—Industrial Lighting Code 

Page 

Introduction- 7 

Section I. Application and Definition--- 8 

Order 2100. Application - 8 

Order 2101. Meaning of Terms--- 8 

Section II. Natural and Artificial Light- 9 

Order 2110. General Requirement- 9 

Order 2111. Natural Light - 9 

Order 2112. Artificial Light- 10 

Order 2113. Shading of Lamps for Overhead Lighting 10 

Order 2114. Shading of Lamps for Local Lighting- 11 

Order 2115. Distribution of Light on the Work- IT 

Order 2116. Emergency Lighting- 11 

Order 2117. Switching and Controlling Apparatus- 12 

Order ,2118. Maintenance- 12 

Part II—Helpful Suggestions on How to Comply With the 
Industrial Lighting Code 

Introduction- 14 

Enforcing the Industrial Lighting Code- 14 

Maximum Production through Good Lighting--- 15 

Desirable Qualities of Artificial Lighting- 16 

How to Plan the Artificial Lighting System- 17 

Mounting Height (Lamps) - 18 

Spacing Between Lamps- 20 

Size of Lamps- 22 

Types of Lighting Units- 23 

R. L. M. Standard Dome Reflector- 24 

Deep Bowl Porcelain Enameled Reflector- 24 

Large Shallow Bowl—Lamp Fitted with Enlarged Opal- 

Glass Cover- 28 

Large Shallow^Bowl—Lamp Fitted with Polished Metal 

Cap- 26 

Mirrored Glass Reflector- 2 6 

Prismatic Glass Reflector- 27 





























6 


TABLE OE CONTENTS 


Page 

Choice of Reflector- 27 

Indirect Lighting -- 32 

Indirect Lighting Computations - 32 

Local Lighting_ 35 

Gas Lighting- 36 

Mercury Vapor Lamps_ 36 

Yard •Lighting_ 38 

Shading of Lamps, for Overhead Lighting-*_ 38 

Shading of Lamps for Local Lighting_„_ 41 

Distribution of Light on the Work_ 43 

Emergency Lighting_ 43 

Electric Emergency_ 44 

Gas Lamps_ 44 

Switching and Controlling Apparatus_ 45 

Maintenance___ 45 

How to Make Lighting Measurements_ 46 

Light Distribution Curves_ 48 



















PART I 


Industrial Lighting Code for Factories, Mills, 
Offices and other Work Places 

INTRODUCTION 

In January, 1913, the Industrial Commission adopted general 
orders on sanitation, which included a group of “shop light¬ 
ing” orders, but experience in enforcing the latter proved 
the desirability of modifying and extending their scope. 

Therefore in July, 1917, the Industrial Commission appointed 
a committee to assist in formulating a revised lighting code for 
factories, mills, offices and other work places. The personnel 
of this committee was as follows: 

P. M. Wicks, Westinghouse Lamp Co., Milwaukee,, Chairman. 

Davis H. Tuck, Illuminating Engineer, U. S. P. H. S. 

J. R. Finn, Cutler-Hammer Co., Milwaukee. 

Howard Ilgner, Bureau of Illumination Service, Milwaukee. 

M. A. Freschl, Holeproof Hosiery Co., Milwaukee. 

Geo. F. Rohn, Electrical Contractor, Milwaukee. 

H. G. Monger, T. M. E. R. & L. Co., Milwaukee. 

R. B. Brown, Milwaukee Gas Light Co., Milwaukee. 

Dr. Claude S. Beebe, Milwaukee. 

John A. Hoeveler, Electrical Engineer,, Industrial Commission, 
Secretary. 

This committee held a number of meetings and consulted the 
following authorities on industrial lighting: 

I. Committee on Lighting Legislation of the Illuminating En¬ 
gineering Society. L. B. Marks, Chairman. 

2. Special Sub-committee of the Illuminating Engineering Society 
appointed to assist Industrial Commission of Wisconsin. Ward Har¬ 
rison, Chairman. 

3. Francis A. Vaughn, Consulting Engineer, Milwaukee. 

4. T. F. Foltz, Mechanical Engineer. Department of Labor and 

Industry of Pennsylvania. 

5. Lewis T. Bryant, Commissioner of Labor of New Jersey. 

6. Arthur J. Sweet, Consulting Engineer, Milwaukee. 

The orders finally formulated by the committee are based 
upon the advice received from these sources and independent 


g INDUSTRIAL COMMISSION OF WISCONSIN 

investigations of committee members. They are definite, clear 
and practical. Hence employers will find them simple and easy 
to apply. 

On May 20, 1918, the Industrial Commission adopted these 
lighting orders pursuant to Sections 2394—41 to 2394—70, in¬ 
clusive of the statutes of Wisconsin. They were published in 
the official state paper on May 27, 1918, and became effective 
on the dates indicated in the orders. Amendments in phrase¬ 
ology were made in Orders 2112 to 2114, inclusive, on October 
17, 1919, which became effective November 24, 1919. Ad¬ 
ditional minor amendments were made on November 20, 1920, 
and these became effective December 20, 1920. 


Industrial Lighting Code for Factories, Mills, 
Offices and Other Work Places 

SECTION I. APPLICATION AND DEFINITIONS. 

Order 2100. Application. This code shall apply as a mini¬ 
mum requirement for the natural and artificial lighting of all 
factories, mills, offices and other work places. 

Order 2101. Meaning of Terms. In this code: 

(1) Candle (or candle-power) means the unit of luminous 
intensity maintained by the national laboratories of the United 
States, France and Great Britain. 

(2) Lumen means the unit of luminous flux equal to the flux 
emitted in a unit solid angle (steradian) by a point source of 
unit candle-power. 

(3) Foot-candle means the unit of illumination equal to one 
lumen per square foot. 

Note: The foot-candle is the lighting effect produced upon an object 
by a lamp of one candle-power at a distance of one foot; at two feet, 
the effect would be not one-half foot-candle, but one-fourth foot-candle; 
at three feet, one-ninth foot-candle, etc. 

(4) Photometer means an instrument suitable for making 
illumination measurements. 

(5) Lamp means that part of the lighting equipment from 
which the light originates. 

Note: With electric lighting it means the incandescent lamp bulb or 
the arc, and with gas lighting, the burner and mantle. 



LIGHTING CODE 


9 


(6) Local Lamps (or Lighting) means lighting units located 
close to the work, and intended to illuminate only a limited 
area about the work. 

(7) Overhead Lamps (or Lighting) means lighting units in¬ 
stalled above ordinary head level to secure a general illumina¬ 
tion over a considerable area. 

(8) Brightness means the intensity of light per unit area 
emitted from or reflected by a body; and in this code is ex¬ 
pressed in candle-power per square inch. 

(9) Glare means any brightness within the field of vision 
of such a character as to cause discomfort, annoyance, inter¬ 
ference with vision, or eye fatigue. 

(10) Eye strain means a physiological condition of the eye 
resulting in discomfort, poor vision or fatigue. 

(11) Shaded means that the lamp is equipped with a re¬ 
flector, shade, enclosing globe, or other accessory for reducing 
the brightness in certain directions, or otherwise altering or 
changing the distribution of light from the lamp. 

SECTION II. NATURAL AND ARTIFICIAL LIGHTING. 

Order 2110. General Requirement. Working or traversed 
spaces in buildings or grounds of places of employment shall be 
supplied during the time of use, with either natural or arti¬ 
ficial light in accordance with the following orders. (2111— 
2118). 

Order 2111. Natural Light. Side windows, skylights, saw¬ 
tooth or other roof lighting construction of buildings shall be 
arranged with reasonably uniform bays and the glass, area so 
apportioned that at the darkest part of any working space, 
when normal exterior daylight conditions obtain, there will 
be available a minimum intensity equal to twice that of Order 
2112 for artificial light. 

Note: Normal exterior daylight conditions obtain when the average 
brightness of the sky is 1.5 candle-power per square inch. 

Awnings, window shades, diffusive or refractive window 
glass shall be used for the purpose of improving daylight con¬ 
ditions or for the avoidance of eye strain wherever the location 
of the work is such that the worker must face large window 


10 


INDUSTRIAL COMMISSION OF WISCONSIN 


areas, through which excessively bright light may at times 
enter the building. 

Note: The intensity requirements for adequate day lighting’ are much 
higher than those for adequate night lighting, because in general under 
daylight conditions, the light coming to the eye from all the surround¬ 
ings in the field of vision is much brighter than at night, and hence a 
correspondingly more intense light must fall on the object viewed. 


Order 2112. Artificial Light. When the natural light is less 
than twice the minimum permissible intensities of illumination 
set forth in the following table, artificial light shall be sup¬ 
plied and maintained in accordance with the table. 

Note: The measurements of illumination at the work will be made 
with a properly standardized portable photometer. 

ILLUMINATION INTENSITV AT THE WORK IN FOOT-CANDLES 


Room or Space to be Illuminated 

Minimum 

Permissible 

Intensities 

(1) 

Intensities 
of Good 
Practice 
(2) 

Produc¬ 

tive 

Intensities 

(3) 

(a) Roadways and yard thoroughfares. 

0.02 

0.05 — 0.25 


(b) Storage spaces. 

0.25 

0.5 — 1. 


(c) Stairways, passageways, aisles. 

0.25 

0.75 — 2. 


(d) Toilets and washrooms. 

0.5 

1.5 3. 


(e) Rough manufacturing such as rough ma¬ 
chining, rough assembling, rough bench 
work, foundry floor work. 

1.25 

2. — 4. 

6. 

(f) Rough manufacturing involving closer 
discrimination of detail. 

2. 

3. - 6. 

10. 

(g) Fine manufacturing such as fine lathe 
work, pattern and tool making, light col¬ 
ored textiles. 

3. 

4. - 8. 

15. 

(h) Special cases of fine work, such as watch 
making, engraving, drafting, dark col¬ 
ored textiles. 

5. 

10. — 15. 

25. 

(i) Office work such as accounting, type¬ 
writing, etc. 

3. 

4. — 8. 

15. 


Note: The intensities listed in column (1) specify the lowest illumina¬ 
tion with which workmen can be expected to work with safety and 
without undue eye strain. 

The intensities listed in column (2) are those employed in well lighted 
modern factories where the aim has been to reduce eye strain to a 
minimum. 

The intensities of column (3) are those employed in factories where 
the management aims at securing* the maximum production and minimum 
spoilage. 

When part daylight and part artificial light must be used together, 
it is particularly necessary to provide high intensity artificial light to 
supplement the inadequate daylight. (See note accompanying Order 
2111 .) 


Order 2113. Shading of Lamps for Overhead Lighting. 

Lamps suspended at elevations above eye level less than one 































LIGHTING CODE 


11 


quarter their distance from any position at which work is per¬ 
formed, shall be shaded in such a manner that the intensity of 
the brightest square inch of visible light source does not ex¬ 
ceed seventy-five candle-power. 

Exception: Lamps suspended at greater elevations than twenty 
ieet above the floor, are not subject to this requirement. 

Note: Glare from lamps or unduly bright surfaces produces eye strain 
and increases the accident hazard. 

The brightness limit specified in this order is an absolute maximum. 
Very much lower brightness limits are necessary in many interiors il¬ 
luminated by overhead lamps, if the illumination is to be satisfactory. 
In some cases, the maximum brightness should not exceed that of the 
sky (1.5 to 3.0 candle-power per square inch). 

Where the principal work is done on polished surfaces, such as pol¬ 
ished metal, celluloid, varnished wood, etc., it is desirable (but not 
mandatory at present) to limit the brightness of the lamps in all down¬ 
ward directions to the amount specified in this order. 


Order 2114. Shading of Lamps for Local Lighting. Lamps 
for local lighting shall be shaded in such manner, that the in¬ 
tensity of the brightest square inch presented to view from any 
position at which work is performed, does not exceed three 
candle-power. 

Note: In the case of lamps used for local lighting, at or near eye 
level, the limits of permissible brightness are much lower than for lamps 
used for overhead lighting, because the eyes are more sensitive to strong 
light received from below, and because such light sources are more con¬ 
stantly in the field of view. 


Order 2115. Distribution of Light on the Work. The re¬ 
flectors or other accessories, mounting height and spacing em¬ 
ployed with lamps shall be such as to secure a reasonably uni¬ 
form distribution of illumination, avoiding objectionable sha¬ 
dows and sharp contrasts of brightness. If local lighting is 
used, there shall be employed in addition, a moderate intensity 
of overhead lighting. 

Note: When local lighting is used as the sole source of illumination 
of an interior, the field of illumination from each lamp is in contrast to 
the surrounding darkness, thereby causing eye strain and increasing the 
accident hazard. 

Order 2116. Emergency Lighting. Emergency lamps shall 
be provided in all work space aisles, stairways, passageways, 
exits, and on all “B” fire escapes (three feet and four inches 
wide—See Building Code), to provide for reliable operation 
when, through accident or other cause, the regular lighting is 
extinguished. Emergency lighting systems, including all 
supply and branch lines, shall be entirely independent of the 


12 


INDUSTRIAL COMMISSION OF WISCONSIN 


regular lighting system and shall be concurrently in operation 
with the regular lighting. 

Note: It is the intention of this order to guard against accident due 
to the failure of the regular lighting system, by providing sufficient 
illumination to enable the occupants to 

1. Avoid contact with moving machinery and other danger points 

until the regular lighting is again put in operation. 

2. To vacate the building safely and expeditiously when this is nec¬ 

essary because of fire or other causes. 

Emergency lighting may be installed in various ways. The method 
to be employed depends upon the size of the premises, the extent of the 
hazards of employment, and the means available for supplying such 
emergency lighting. (See Part II, page 44.) 


Order 2117. Switching and Controlling Apparatus. Switch¬ 
ing or controlling apparatus shall be so placed that at least 
pilot or night lights, which may be part of the emergency 
lighting system, may be turned on at one or more easily ac¬ 
cessible points. All such apparatus shall be plainly labeled 
for identification. ' i 

Note: The purpose of this order is to make it possible for the night 
watchman or other qualified persons to turn on enough lamps, when en¬ 
tering any portion of the premises at night, to enable them to safely 
see their way around without the need of a lantern or flashlight. 


Order 2118. Maintenance. Windows and artificial lighting 
units shall be cleaned at sufficiently frequent intervals to main¬ 
tain illumination in accordance with the standards of these or¬ 
ders. All parts of the artificial lighting system shall be fre¬ 
quently inspected and when found defective, replaced or re¬ 
paired. 

Note: Lamps with heavily blackened bulbs should be replaced even 
though they may still burn. 


LIGHTING CODE 


13 




Pig. 3—Best ©ye protection is secured by completely concealing the light source. In this hosiery 
mill gas-filled tungsten lamps are equipped with indirect bowls. Although the indirect system may 
be more expensive in initial cost and operation, the immensely improved quality of illumination justi¬ 
fies its use in factories where high grade work is done and the best illumination obtainable is essen- 

















14 


INDUSTRIAL COMMISSION OF WISCONSIN 


PART II 

Helpful Suggestions on How to Comply with 
the Industrial Lighting Code 

By 

John A. Hoeveler, Electrical Engineer, Industrial 
Commission of Wisconsin. 

Introduction 

Acknowledgment is due Mr. R. B. Brown of the Milwaukee 
Gas Light Co. for the data on gas lighting; to Mr. Arthur J. 
Sweet, Consulting Engineer, Milwaukee, Davis H. Tuck, Elec¬ 
trical Engineer, Holophane Glass Co. Inc., New York and the 
engineering department of the National Lamp Works, Cleve¬ 
land, Ohio, for assistance in preparing the discussion on re* 
hectors and their application; to Mr. George C. Keech of the 
Cooper Hewitt Electric Company, Chicago, for data on the 
mercury vapor lamp, to Mr. Francis A. Vaughn, Vaughn and 
Meyer, Consulting Engineers, Milwaukee, for many helpful 
suggestions on various aspects of the work. 

Enforcing the Industrial Lighting Code. 

It is not assumed that a factory owner or manager should 
study the details of the science of illumination, to the extent 
of understanding the provisions of this industrial lighting 
code, any more than he should he required to know the details 
of building construction and the rules of the building code. 
No factory manager would attempt to do this. When he con¬ 
templates constructing a new building, he calls in an archi¬ 
tect, explains his requirements and gives, the architect 
authority to proceed. However, knowing that the state regu¬ 
lates building construction, he instructs his architect to carry 
out the provisions of the building code, with which the archi¬ 
tect is expected to he familiar. In the same way, the lighting 
of the factory must be put up to those whose business it is 
to know and understand the provisions of the lighting code. 


LIGHTING CODE 


15 


Provision for natural lighting must be made when the 
building is planned and this, as a rule, is the architect’s work. 
In general, therefore, it becomes the architect’s duty to see 
that the provisions of the lighting code are complied with in 
respect to natural lighting. 

Provision for the artificial illumination, should preferably 
be made before building construction is commenced, at the 
time the building and the arrangement of machinery or other 
equipment is planned. Some one competent to interpret the 
provisions of the lighting code should be in charge of this 
work. If the owner leaves this to the architect, he should 
assure himself that the architect has someone in his employ 
competent to do the work, or that the architect will engage 
the services of an illuminating engineer. The competent inde¬ 
pendent consulting engineer will more than earn his fee in the 
savings he can effect through his specialized knowledge in the 
lighting field. If the factory manager personally undertakes 
to decide as to the lighting system to be employed, or if he 
places this responsibility upon his electrical department, he 
should at least avail himself of such commercial engineering 
services as can usually be obtained from the local central sta¬ 
tion, from first class electrical contractors or from reliable 
manufacturers of lighting equipment. 

Maximum Production Through Good Lighting, 

The industrial manager should clearly recognize the func¬ 
tion of this or indeed of any lighting code. It does not specify * 
the lighting practice which will insure the maximum produc¬ 
tion and minimum spoilage; on the contrary, it establishes the 
minimum lighting service which will sufficiently safeguard the 
safety and health of the employes. In practically all cases, 
the industrial manager will find it highly profitable to provide 
materially better lighting than that which will barely meet 
the requirements of this code. At least the intensities of col¬ 
umn (2) in the table of Order 2112 (See page 10) should be 
employed, and if the benefits of increased production are to 
be realized in a marked degree, the intensities of column (3) 
should be used. 

The failure to realize that really adequate lighting is some¬ 
thing more than providing a sufficient quantity of light is to¬ 
day costing industrial America annual losses which can con- 



16 INDUSTRIAL COMMISSION OF WISCONSIN 


servatively be stated as totaling many millions. Maximum pro¬ 
duction of the worker depends not only upon providing a suf¬ 
ficient quantity of light, but upon proper quality of light, 
proper direction on the work, freedom from objectionable 
shadows and conditions suitable for the eye to perform its 
functions without excessive fatigue. 


Fig. 4—“Looping” is a knitting operation requiring the best il¬ 
lumination obtainable. Ten foot candles on the horizontal plane, 
on a level of the work, provide such satisfactory results that the 
operators prefer the artificial light to the daylight. 


While the Industrial Commission cannot undertake to give 
each plant the specialized individual study needed to design an 
adequate lighting system for it, the commission will gladly give 
expert advice covering the broad outlines of any problem. 
Then if the services of a good electrician are secured to carry 
out the details of this advice, a good installation will be as¬ 
sured. 


Desirable Qualities of Artificial Lighting. 

In addition to adequate intensity of illumination at the 
work, whether in horizontal, vertical or oblique planes, mod¬ 
erate intensities of illumination in aisles and other spaces inter- 




LIGHTING CODE 


17 


mediate between the working surfaces, on tbe walls, ceilings, 
etc., are necessary to safety and comfortable vision. 

The use of extremely bright light sources must be scrupu¬ 
lously avoided, otherwise there will be harmful glare. More¬ 
over, strong contrasts of brightness should be avoided for the 
same reason. Well shaded lamps and light walls, moderately 
illuminated, will minimize the eye strain. 

Reflected images of light sources in polished surfaces must 
be guarded against by the use of lighting units which reduce 
the brightness of the lamps sufficiently in the downward di¬ 
rections. Such images, from excessively bright light sources, 
cause extremely trying glare, because of the necessity of di¬ 
recting the eyes toward those surfaces, and because the eyes 
are by nature especially sensitive to light from below. 

To be satisfactory, the illumination must be such that there 
are no shadows so dense as to make vision difficult, where the 
light from one or two sources is cut off, nor so sharply defined 
as to cause confusion between a machine part and its shadow. 
Shadows should be soft and luminous. 

In some cases color forms one of the most important aids to 
vision. The ideal source of light emits rays of all colors. 
Ordinary incandescent lamps give a yellowish light, but all 
colors are present in sufficient quantity 'to preserve the natural 
appearance of objects. Where exact color discrimination or 
better identification of detail through color contrasts is es*. 
sential, the gas filled tungsten lamp having the blue bulb will 
be found useful. The blue bulb serves to screen out the excess 
red and yellow rays. - 

How to Plan the Artificial Lighting System. 

Since this code requires the use of overhead lighting, even 
where local lighting is used as the principal source of illumi¬ 
nation, it becomes necessary for those, upon whom falls, the 
responsibility of designing lighting installations, to know how 
to meet the code requirements. A few helpful suggestions are 
therefore given. 

In planning an artificial lighting system, the decision must 
first be made as to type of light source to be employed. Three 
types of light sources are today in general use in industrial 
lighting—the incandescent electric lamp, the mercury-vapor 
electric lamp and the mantle gas lamp. Each of these has its 


18 


INDUSTRIAL. COMMISSION OF WISCONSIN 


merits. The mercury-vapor lamp is. supplied by only one man¬ 
ufacturer, and this manufacturer designs the installations of 
his product. The following discussion of size of lamp neces¬ 
sary ito meet Order 2112 is, therefore drafted with particular 
reference to the electric incandescent lamp and to the mantle 
gas lamp. 

The determination of the size of lamp required to supply the 
specified intensity is dependent upon the spacing between light 
sources, and this involves a simultaneous consideration of 
Order 2115, ‘‘Distribution of Light on the Work.” In de¬ 
termining the size of lamp, whether gas or electric, four items 
must be considered: 

(a) At what height shall lamps be mounted? 

(b) How far apart shall lamps be spaced? 

(c) What size of lamp shall be\ used? 

(d) What kind of reflector or globe shall be used? 

Mounting Height. (Lamps.) 

It will generally be found desirable to mount lamps as, high 
as possible. The chief exceptions to this general rule consist 
of those cases (a) where the ceiling is very high relative to 
one dimension of the floor area, (b) where horizontal beams, 
belting or the like form a network at some distance below the 
ceiling, (c) where it is necessary to place lamps with ref¬ 
erence to machines in order to get proper direction of light on 
the work, and (d) where a high diffusion is desired and this 
can best be attained by the use of diffusing type lighting units 
suspended relatively close to the work. The incandescent elec¬ 
tric lamp can generally be mounted directly on the ceiling, 
thus bringing the light center from 6 inches to 12 inches below 
the ceiling. The minimum distance below the ceiling at which 
the mantle gas lamp can be mounted varies somewhat with the 
size of lamp and somewhat with the character of the ceiling. 
The use of a heat deflector permits the lamp to be mounted 
closer to wood, plaster or metal ceilings, and such use is there¬ 
fore recommended. When such deflector is used, the light 
center of mantle gas lamps can be brought from 18 inches to 
35 inches from the ceiling. 

There are two chief advantages of mounting lamps as high 
as possible. First, higher mounting heights permit the use of 
wider spacings with equally good distribution of the light, 


LIGHTING CODE 


19 



Note: This chart refers to illumination on a horizontal plane 36 
inches above the floor. 


;nca a,\ ^ - -- 

Type B means vacuum tungsten 
lamp. 


Type C means gas filled tungsten 
lamp. 


Plate I—Electric Lighting 


For determining the proper spacing and size of incandescent 
tungsten lamps to produce any desired intensity of illumination. 





















































































































































































































































































































20 


INDUSTRIAL COMMISSION OF WISCONSIN 


such wider spacings in turn resulting in the use of a smaller 
number of lamps of larger size. This means lower installation 
and operation costs. A second advantage of higher mounting 
heights is that nearby lamps are less likely to come within the 
direct field of vision, and hence are less likely to be a source of 
eye fatigue and eyestrain to the worker. 

&'pacing between Lamps. 

The upper part of Plates I and II present the data from 
which the proper spacing between lamps can be satisfactorily 
determined for the more typical or common conditions of in¬ 
stallation. The method of such determination is illustrated by 
the following example: 

Example: Let it be assumed that the ceiling height is 10 
feet and that the above recommendations to mount the lamps 
as close as possible to the ceiling will be followed. Referring 
to Plate I, the fine horizontal line representing a 10 foot ceiling 
height is followed to its intersections with the vertical lines. 
The first and last of these intersected vertical lines, show that 
the lamps need not be mounted closer together than 8 feet and 
should not be mounted further apart than 12%- feet. The best 
spacing will be the minimum of these values—in this case 8 
feet. If the work is of an exacting character, the spacing 
should approximate this best value—in this case should not be 
greater than, say, 10 feet. If the work is not of an exacting 
character, ^ wider spacing may be employed, but not greater 
than the maximum indicated by the chart. 

The exact spacing adopted will generally depend upon the 
dimensions of the building structure. Thus in the case of the 
ceiling height assumed above, if the factory building has bays 
whose dimensions are 20 feet by 20 feet lamps would preferably 
be located on 10 foot centers in both directions, thus providing 
4 lamps per bay. 

It should be noted that in Plate I the proper spacing of 
lamps is determined with respect to the ceiling height, while 
in Plate II the spacing is determined with relation to the 
height of the gas mantle above the floor. This different basis 
of reference is made necessary by the variations in minimum 
distance at which the gas lamp can be mounted below the ceil¬ 
ing. Of course, in those cases where the electric lamps are 


Heiomt of Mantle above Floor, in Feet. 


LIGHTING CODE 


21 


30 


2 a 


Z 6 


ZA 


zz 


16 


14 


12 


1 0 



Width or Band Represents 
Variation in Illumination with 
Adjustment or Burner. 


Lamp ErncltN 
u uuy i . 191 a . 


ESPECIALLY PREPARED FOR 

Industrial Commission of Wisconsin. 


BY 

Arthur J- 5weet 

CONSULTING ENCIMEE* 
M:i,V' 1 aukee. 


Plate II—Gas Lighting 

Note: This chart refers to illumination on a horizontal plane 3 6 

inches above the floor. 

For determining the proper spacing and size of gas lamp to pro¬ 
duce any desired intensity of illumination. 












































































































































































































































































































































22 


INDUSTRIAL COMMISSION OF WISCONSIN 


suspended at a considerable distance below the ceiling, the 
spacing should be determined with respect to the mounting 
height of the lamps. 

Plates I and II are computed with reference to a horizontal 
plane 3 feet above the floor. The data is, however, sufficiently 
accurate for relatively small office interiors where the working 
plane is usually 2-^ feet above the floor. It is also sufficiently 
accurate for large interiors when the working plane is at any 
lesser distance than 3 feet from the floor. 

Size of Lamps. 

The lower portions of Plates I and II present the data from 
which may be determined the size of lamp necessary to produce 
the specified intensity of illumination. Thus under the condi¬ 
tions of installation assumed in the above example, with lamps 
spaced 10 feet apart, let it now be assumed that the work is 
of such a character that, an illumination of 10 foot-candles is 
desired. Let it further be assumed that the incandescent 
electric lamp will be employed. Referring now to the lower 
portion of Plate I, the vertical line representing a 10 foot sep¬ 
aration is followed to its intersection with the curved line rep¬ 
resenting 10 foot-candles. It is found that this occurs in the 
band representing the 150 watt lamp. This means that, if 
the more efficient types of reflector (Figs. 5, 11 and 12) be em¬ 
ployed, the 150 watt lamp on 10 foot spacing will produce an 
average horizontal illumination of 10 foot-candles. If, how¬ 
ever, the less efficient types of reflector (Figs. 7, 8, and 10) be 
employed, the 150 watt lamp will produce an illumination of 
about 8 foot-candles. Therefore, if it be desired to secure an 
illumination not less than 10 foot-candles and it is also desired 
to use one of the less efficient types of reflectors (Figs. 7, 8 and 
10), it becomes necessary to use the next larger size of lamp, 
i. e. the 200 watt size. 

The charts of Plates I and II allow a 30% factor for depre¬ 
ciation due to dirt on the reflector or lamp, or to deterioration 
of the filament or mantle in light giving power. With reason-* 
able attention to maintenance, the lighting system can be main¬ 
tained at a maximum depreciation not exceeding 30%. If, 
however, proper maintenance is not afforded, it will be neces¬ 
sary to employ larger lamps than those indicated by the charts. 


LIGHTING CODE 


23 


It must be clearly realized that the charts of Plates I and II 
determine the size of lamp with reference to horizontal illumi¬ 
nation. Order 2112, however, specifies the illumination at the 
work. If the work be chiefly on a horizontal plane, the charts 
may be directly used to determine the proper 'size of lamp with 
reasonable accuracy and exactness. If, however, the work be 
chiefly in some vertical plane, the problem of proper lamp size 
becomes much more complicated and can only be roughly de¬ 
termined by any general data. The ratio between the hori¬ 
zontal illumination and the vertical illumination depends 
chiefly on two factors,—(a) to what degree the light units are 
in front of the work, so that their light can illuminate the face 
of the work; and (b) the type of lighting unit employed. The 
first of these factors so depends upon local conditions that no 
general data of value can be given thereon. As for the second 
factor, the approximate ratio between the vertical and the 
horizontal illuminations are given for the various distinct types 
of reflectors 'in Table II. (Page 32.) These relations are 
necessarily approximate, since they vary considerably with 
varying conditions of installation. They vary but slightly, 
however, as between different makes of the same type of re¬ 
flector. 

Types of Lighting Units. (See also Figs. 15, 16, 19, 20 and 21). 

It is only under most unusual conditions that the use of 
naked incandescent lamps will meet the requirements of good 
lighting and seldom will their use be permitted by the code. 
Therefore it becomes necessary to carefully select reflecting 
and diffusing accessories, which will modify the distribution 
of light from the lamps so as to secure reasonably uniform 
illumination on the working surfaces and surroundings, to re¬ 
duce glare, to soften shadows,, and to utilize the light eco¬ 
nomically. 

For factory lighting there are at present five distinct types 
of reflectors (Figs. 5, 7, 8, 10, 11 and 12) which are especially 
worthy of consideration. 

Special conditions sometimes make desirable the use of 
special types of reflectors, as for instance, the angle type of 
porcelain-enameled metal reflector or the concentrating pris¬ 
matic and mirrored glass reflectors. The proper use of such 


24 


INDUSTRIAL. COMMISSION OF WISCONSIN 


special types depends so largely on local conditions that no 
general data of value thereon can be given. 

R. L. M. Standard Dome Reflector. (Fig. 5) 

The R. L. M. Dome is a porcelain enameled reflector. The 
permanence of this material even under unfavorable atmos¬ 
pheric conditions, its moderate cost, and the ease with which 
it can be kept clean, make it highly useful for industrial pur¬ 
poses. The enamel coating must be dense so that as little light 
as possible will penetrate to the steel, since all light that 
reaches the steel backing is absorbed and therefore wasted. 
Enamels vary in efficiency; if of two reflectors one appears 
grayish or bluish in comparison with the other, it is sure to be 
considerably lower in efficiency. 

The output of typical reflectors is 75 to 80 per cent of the 
light produced by the lamp. The eye is shielded from direct 
glare in a manner which will more than meet the requirements 
of Order 2113. The large area of the reflector tends to reduce 
the harshness of shadows, and the light distribution is such as 
to provide high illumination on vertical surfaces as well as on 
horizontal surfaces. (See Tables I and II.) 

Clear bulb lamps should not be used with this reflector on 
mounting heights of less than 20 feet; bowl-frosting the lamps 
will usually be sufficient where protection against direct glare 
only is necessary, but where protection against reflected glare 
must be had, opal-glass caps or lamps with bowls enameled 
should be used. (Figs. 6 and 9.) 

Deep Bowl Reflector—Porcelain Enameled. (Fig. 7) 

The deep bowl of Fig. 7 also is a porcelain-enameled re¬ 
flector. The output of typical reflectors is about 65 per cent 
of the light produced by the lamp. This reflector gives a max¬ 
imum shielding of the lamp filament, but in no way modifies 
the brightness of the images of the lamp filament reflected from 
polished surfaces. Moreover the surface from which the light 
is received is so limited that shadows are sharp. Some dif¬ 
fusion of the light coming directly from the lamp can be at¬ 
tained by the use of bowl-frosted lamps, but this scarcely 
reduces reflected glare from polished surfaces adequately. 
Since opal-glass caps or bowl-enameled lamps would cause a 
very great loss of light if used with this reflector, the unit is 


LIGHTING CODES 


25 



Fig. 5—R. L. M. 
Standard Dome. 



Fig. 6 — Opal-Glass Cap. 



Fig. 7—Deep Bowl 
Porcelain Enameled. 



Fig. 8—Large Shallow Bowl. 
Lamp Fitted with Enlarged Opal- 
Glass Cover. 



Fig. 9—Bowl Enam¬ 
eled Lamp. 



Fig. 10—Large Shallow Bowl. 
Lamp Fitted with Polished Metal 
Cap. 












26 


INDUSTRIAL COMMISSION OF WISCONSIN 


out of the question where work is done on polished surfaces. 
The chief use for this reflector is for somewhat localized light¬ 
ing over benches and tables,. 

Large Shallow-Bowl. Lamp Fitted with Enlarged Opal-Glass 
Cover. (Fig. 8) 

This unit likewise is porcelain-enameled. The diameter of 
the reflector is very much greater than that of the E. L. 1\1. 
Dome, running as high as 22 inches in the largest size avail¬ 
able (for 300 watt lamp). The lamp is surrounded by a clear 
glass cylinder with the lower end rounded and enameled to re¬ 
flect and diffuse the light. The area of the enameled portion 
is greater than that of an opal cap (Fig. 6), which together 
with the large surface of the reflector results in a very low 
brightness, making this unit highly desirable where softened 
shadows and the maximum freedom from reflected glare are 
important elements. The construction also prevents dust from 
settling on the lamp or within the cylinder, thus simplifying 
maintenance. The output is about the same as that of the deep 
bowl porcelain-enameled reflector. 

Large Shallow-Bowl. Lamp Fitted with Polished Metal-Cap. 
(Fig. 10) 

This unit is quite similar to the previously described one 
(Fig. 8). It differs in that a metal-cap is placed over the bowl 
of the lamp. This cap intercepts and reflects the light against 
the porcelain-enameled surface, where it is thoroughly dif¬ 
fused and directed to the work. The output is approximately 
the same as for the deep bowl porcelain-enameled reflector. 
The unit has the disadvantage of a cap which deteriorates in 
time, and requires renewing. 

Mirrored Glass Reflector—Deep Bowl. (Fig. 11) 

This type of reflector is made of clear glass blown in the 
shape of a reflector, on the exterior surface of which a thin 
layer of silver is coated and this in turn covered by a protec¬ 
tive enamel. To eliminate the brilliant images of the lamp 
filament, or striations, which would appear on the surface il¬ 
luminated, the reflector surface is corrugated. 

Such mirror reflectors are highly efficient, in typical reflect¬ 
ors having an output as high as 85 per cent of the light pro- 


LIGHTING CODE 


27 


duced by the lamp, because the light passes through clear 
glass to a silver surface, one of the best reflecting surfaces 
known, and therefore find wide application for both direct and 
indirect illumination in factories and offices. They are made 
in the deep-bowl shape for industrial lighting purposes, and 
their use is limited in the same manner as the deep-bowl por¬ 
celain-enameled reflector. Special concentrated mirrored glass 
reflectors are very effective in the lighting of high interiors 
such as monitors. Because of the corrugations more labor is 
required to keep these reflectors clean. 

Prismatic Glass Reflector—Beep Bowl. (Fig. 12) 

This type of reflector is made of clear glass with many small 
prisms composing the entire body of the reflector. The prin¬ 
ciple involved is that of total reflection from properly designed 
prisms. Since the light is reflected by clear glass only, the ab¬ 
sorption is low and the efficiency of these reflectors very high, 
typical reflectors having an output as high as 75 per cent of 
the light produced by the lamp. They are made in the deep- 
bowl shape for industrial lighting purposes. Since 15 to 20 
per cent of the light is transmitted above the horizontal, these 
reflectors brighten the ceilings and walls, thereby giving the 
room a cheerful appearance and somewhat softening shadows. 
As in the case of mirrored glass reflectors a strongly concen¬ 
trated light distribution is obtainable for use in high interiors. 
The distribution of light from the reflector, illustrated in Fig. 
12, produces a higher illumination on vertical surfaces than is 
obtainable with any other type of reflector available at present. 
More labor is required to keep these reflectors clean than in 
the case of reflectors with a smooth surface. Unless bowl- 
frosted lamps are used, these reflectors should not be used 
where the work is on polished surfaces. 

Choice of Reflector. 

From Plate 1 it is apparent that the type of reflector used 
with electric incandescent lamps affects the size of lamp re^ 
quired because of the difference in efficiency of the various 
reflectors. But the type of reflector to be used cannot be de¬ 
cided on the efficiency basis alone. Other important factors 
are the appearance that the lighted room makes, the amount 
of direct glare and reflected glare, the character of the shad- 


28 


INDUSTRIAL COMMISSION OF WISCONSIN 


ows, and the ease of maintenance. In Table I, the five types of 
industrial units, are rated with respect to these seven require¬ 
ments. All of these items should be carefully considered when 
the type of reflector is chosen for any room or space. The 
importance of the various qualities, is different for different 
purposes. Thus in an aluminum utensil manufacturing plant, 
the elimination of reflected glare is of first importance, where¬ 
as in a packing and shipping room it is of slight importance. 

The approximate ratio between the vertical and the horizon¬ 
tal illumination produced by the various reflectors is. given in 
Table II. (See also Page 23). 




flector— Deep Bowl. 



Fig. 12—Prismatic Glass Re¬ 
flector—Deep Bowl. 







TABLE I- RATING OF REFLECTORS ACCORDING TO QUALITIES 


LIGHTING CODE 


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Large 

Shallow 

Bowl 

Lamp Fit¬ 
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cap Fig. 

8 and 10 

Good 

Good 

Good 

Excellent 

Very good 

Best 

Fair 

Deep 
Bowl 
Fig. 7 
Bowl- 
Frosted 
Lamp 

Good 

Good 

Poor 

Good 

Poo r 

Fair 

Very good 

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Bowl 
Fig. 7 
Clear 
Lamp 

Very good 

Good 

Poor 

Fail- 

Con¬ 

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Poor 

Excellent 

R. L. M, 
Standard 
Dome 
Fig. 5 
Bowl- 
Enameled 
Lamp 

Very good 

Very good 

Good 

Excellent 

Good 

Excellent 

Fair 

R. L. M. 
Standard 
Dome 
Fig. 5 
Bowl- 
Frosted 
Lamp 

Excellent 

Excellent 

Good 

Good 

Poor 

• 

Good 

Very good 

R. L. M. 
Standard 
Dome 
Fig. 5 
Clear 
Lamp 

Best 

Best 

Fair 

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Fig. 13—In this assembly room an intensity of 15 foot-candles on the horizontal plane at the level 
of the chassais is provided. This is five times as much as the code demands, but it enables production 
to go along at the usual rate even after the daylight is gone. 










LIGHTING CODE 


31 


i 



Fig. 14_Knitting room of a hosiery mill, in which lighting units of the type illustrated in Fig. 8 are 

used. Illumination is 10 foot-candles on 36 inch horizontal plane and 5 foot-candles on vertical plane at 
same elevation. It is an excellent installation. The small lamps at the ceiling are the emergency lights 
called for by Order 2116. 





























32 


INDUSTRIAL COMMISSION OF WISCONSIN 


TABLE II—APPROXIMATE RATIO BETWEEN THE VERTICAL AND THE 

HORIZONTAL ILLUMINATION 


Type of Reflector 

Vertical 
Illumination 
in per cent of 
Horizontal 
Illumination 

Correction Factor 
to be applied to size 
of lamp when Plate 

I is used for vertical 
illumination deter¬ 
mination 

Deep-bowl prismatic-glass reflector Special In¬ 
dustrial unit. Fig. 12. 

55% 

1.82 

R. L. M. Standard Dome porcelain-enameled 
metal reflector, Fig. 5. 

50% 

2.00 

Deep-bowl mirrored glass reflector, Fig 11. 

45% 

2.23 

Large shallow-bowl porcelain-enameled reflec¬ 
tor-lamp fitted with shield or cap, of metal or 
opal glass, Figs. 8 and 10. 

45% 

2.23 

Deep-bowl porcelain-enameled metal reflector, 
Fig. 7... 

45% 

2.23 


Note:—“Horizontal illumination” refers, of course, to the illumination produced 
on a horizontal plane. In like manner, “vertical illumination” refers to the illumin¬ 
ation produced on a vertical plane. 

In using 1 this table, first obtain the proper spacing 1 and size of lamp from Plate I: 
then to get correct lamp size to give the desired intensity of illumination on vertical 
surfaces multiply by the “correction factor” above. 

Indirect Lighting. (Figs. 15 and 16) 

All of the foregoing discussion and data pertains to direct 
lighting in industrial service. During recent years, however, 
there has been a growing tendency to employ indirect lighting 
for certain classes of work in the textile industry. Wisconsin 
industries were pioneers in this movement. The advantages are 
the complete elimination of direct glare, the almost complete 
elimination of reflected glare, the very good appearance of the 
lighted room, the elimination of objectionable shadows and in¬ 
deed the almost complete elimination of shadows. The disad¬ 
vantages are poor efficiency and more expense for maintenance. 
The conclusion must not be drawn, however, that indirect light¬ 
ing is ideal for all classes of service. Illumination of too dif¬ 
fuse a character is undesirable where a directed light is needed 
as for manufacturing where the work is on surfaces in many 
planes. 


Indirect Lighting Computations. 

Proper spacing of indirect units may be easily determined as 
follows: Subtract 3 feet from ceiling height of the room; 















LIGHTING CODE 


33 


multiply the result by 1.8 to determine the best spacing; or 
multiply by 2.4 to determine the widest permissible spacing. 
In general, sufficiently satisfactory results will be obtained if 
the spacing does not exceed twice the value obtained by sub¬ 
tracting 3 feet from the ceiling height. For the same size of 
lamp indirect lighting units will produce about 60 per cent the 
illumination on a 36 inch horizontal plane secured with the 
R. L. M. Standard Dome porcelain-enameled reflector, provided 
the ceiling finish is white. 

By comparison of the above rule with the data presented in 
Plates I and II, it will be noted that light units may be spaced 
considerably further apart when indirect lighting is employed 
than when direct lighting is employed. This results in the use 
of fewer light units; so that while the cost of one indirect unit 
is greater than that of one direct unit, the total cost of instal¬ 
lation is usually approximately the same. 

Indirect units should be mounted at such distance below the 
ceiling that the entire ceiling is lighted to an approximately 
uniform degree. Figures 15 and 16 illustrate two commonly 
used types of indirect fixtures. 



pig 15 .—Porcelain-enameled bowl type of indirect fixture. 
Bowl itself acts as reflector. 






34 


INDUSTRIAL COMMISSION OF WISCONSIN 



Fig. 16.—Indirect fixture provided with auxiliary mirrored 
glass reflector. 



Fig. 17.—Five mantle gas lamp 

























LIGHTING CODE 


35 


Local Lighting. 

As previously stated local lighting solely is not permitted 
by this code, and in any event is undesirable and is therefore 
to be avoided if possible. Local lighting is always objection¬ 
able because of the sharp contrasts in intensity which are in¬ 
herent with the system; because small and inefficient lamps 
must be used which are of a size adopted for use in the home 
and therefore are subject to theft; because it is difficult to 
keep them properly adjusted in the reflectors. Maintenance 
of local lighting systems is known to be high; reflectors and 
lamps are very much more rapidly soiled than with overhead 
lighting; lamps are broken and reflectors bent or totally dis¬ 
carded; workmen substitute larger lamps than the reflectors 
will properly provide shading for; the local light of one work¬ 
man is likely to be adjusted so as to shine in another man’s 
face. 

There are, however, some instances in which an operation re¬ 
quires some supplementary local illumination. No general pro¬ 
cedure for calculating the size and location of units can be for¬ 
mulated because of the many different conditions encountered. 
It is seldom necessary to use lamps larger than 50 watts, and 
smaller lamps usually will be adequate. It is difficult and 
costly, for instance, to illuminate stitching operations with 



Fig. 18—Adjustable Fixture for Local Lighting of Stitching Opera¬ 
tions. 

overhead lighting only. Here a local unit of 15 watt size 
(Fig. 18) supplements the overhead lighting. Notice that a 
fixture is used which keeps the light adjusted to the proper 
position. Flexible drop cords are incapable of doing this. 







36 


INDUSTRIAL COMMISSION OF WISCONSIN 


Gas lighting (Fig. 17) 

The use of gas lighting has formerly been handicapped by 
lack of adaptability, difficulty of maintenance, and poor plan¬ 
ning. Recent developments in efficient mantle gas units, 
equipped with well designed reflectors, are worthy of consider¬ 
ation. The installation cost of a first-class mantle gas and of 
a first-class electric installation are approximately the same; 
operating costs vary in different localities, depending on the 
price of gas and electric current. The reliability of gas serv¬ 
ice has encouraged its use for emergency lights. As will be 
noted from Plate II, three sizes of gas mantle lamps are avail¬ 
able: single mantle, three mantle and five mantle. 



Fig. 1'9—Laundry illuminated by five.mantle gas arcs 
Fig. 17.) 


{See also 


Mercury Vapor Lamps. (Fig. 20) 

The use of mercury vapor lamps has already been suggested. 
This lamp consists of a glass tube one inch in diameter and 
from twenty to fifty inches long. One end of the tube, en¬ 
larged into a bulb (Fig. 20) for holding metallic mercury, and 
a small metal cup at the other end serve as electrodes or car¬ 
riers to the electric current, which is supplied to them through 





LIGHTING CODE 


37 


lead in wires sealed into the glass. The tube contains, no air 
or other gas, so that when an electric current is caused to pass 
from one electrode to the other, it vaporizes a small quantity 
of the mercury, which fills the tube. The vapor is, rendered 
luminous by the passage of the current, thereby giving forth 
light of a peculiar peacock-blue color. The lamp gives off 
mainly yellow-green and blue rays. In addition to the tube, 
a commercial type of mercury-vapor lamp consists of the neces¬ 
sary electrical accessories for starting the flow of current, 
when the lamp is turned on, and maintaining it in steady 
operation. 



The peculiar color composition of the light gives it distinct 
value for industrial purposes. 

(1) It enables the eye to see small objects and fine detail with 
great sharpness. 

(2) It enables the eye to see distinctly with low illumination, be¬ 
cause of this sharpness of vision, thereby rendering objects in 
shadows visible. 

(3) It is easy on the eyes because of the low brightness of the 
tube (14.9 candle-power per square inch). This brightness, al¬ 
though well within the maximum permissible for overhead light¬ 
ing, under the conditions of Order 2113, nevertheless may cause 
fatigue, when lamps are installed at low elevations and not shaded 
properly.* 

(4) Shadows are softened. 

(5) Because of the low brightness of the tube, jmages of the 
lamp in polished surfaces are much less harmful than for most 
other types of lamps, which have not been well shaded in all down¬ 
ward directions. 

As previously stated, calculations for installations employ¬ 
ing these lamps will not be given here. Factory managers in- 



38 


INDUSTRIAL COMMISSION OF WISCONSIN 


terested may get advice from consulting engineers or the 
manufacturers of the lamp. Their correct use requires inti¬ 
mate knowledge of the lamp and its construction, which makes 
it impossible to give instructions for their use in a bulletin of 
this type. 

Yard Lighting. (Fig. 26) 

Although the illumination required in yards is of a much 
lower order of intensity, the same general principles apply as 
for interior lighting. In general lamps may be installed far¬ 
ther apart than for interior lighting, hy using special widely 
distributing reflectors, but care must be exercised that the 
illumination at any point is secured from more than one di¬ 
rection, otherwise there may be deep shadows cast, where there 
ought to be light to reveal danger points. This sets certain 
limitations upon the area it is desirable to attempt to illumin¬ 
ate from a single source. Yard lighting lamps should be 
mounted at least 20 feet above the ground level, higher if pos¬ 
sible, to shorten the shadows and minimize glare. If the lamps 
must be installed lower than 20 feet, lamps larger than 100 
watts should not be used. R. L. M. Standard Dome porcelain- 
enameled reflectors, Fig. 5, of the weatherproof type, may be 
used to good effect, but the spacing between units should not 
exceed four times the height above the ground. Prismatic 
refractor units, Fig. 21, permit a spacing between units of eight 
times the height above the ground. 

Shading of Lamps for Overhead Lighting. The provisions 
of Order 2113 can best be illustrated by the diagram of Fig. 22. 
The most distant light source, from the workman, is shown at 
A. It is elevated 6' 0" above eye-level, which is less than one- 
fourth the distance from the eye, 53 feet. This lamp then 
must be shaded as specified in the order. If it were elevated 
to position B, which is 13' 3" above eye-level, it would not re¬ 
quire shading to comply with this order. 

In large interiors with low ceilings,, it is not possible to ele¬ 
vate lamps iso as not to require shading. It then becomes 
necessary to use a reflector that screens off all direct view of 
the luminous element (tungsten filament or gas mantle) in the 
limiting angle of 14 degrees below the horizontal. All well 
designed dome reflectors provide a screening angle greater 


LIGHTING CODE 


39 


than 14 degrees; whereas the deep-bowl types provide a still 
greater screening angle (in some cases 30 degrees). Almost 
any of the commonly used types of reflecting glassware, such 
as prismatic glass and opalescent glass, will reduce the bright¬ 
ness of the light source to that specified in the order, and the 
opaque reflecting media, porcelain-ienameled steel and mirrored 
glass, completely screen the light source. 

While the use of proper reflectors or other suitable acces- 



Fig. 21—Prismatic refractor yard lighting fixture permits broadest 
spacing of lamps. 


sories is made mandatory under certain conditions, they should 
be used, even where not required by the code, for economy 
sake. With a well designed and efficient reflector, the illumin¬ 
ation at the work may be increased as much as 60 per cent 
over what the bare lamp will provide. 

Where the principal work is done on polished surfaces, 
images of the lamp in these surfaces prove nearly as distress¬ 
ing as the lamps themselves, and are much more difficult to 









INDUSTRIAL COMMISSION OF WISCONSIN 


40 



Fig. 22—This diagram illustrates the provisions of Order 2113, Shading of Lamps for Overhead Lighting 
• Note: The reflector contour shown above does not indicate a preference on the part of the Industrial commission 
Other contours providing the same minimum screening angle will conform to the requirements of this order 












































LIGHTING CODE 


41 


avoid. In such circumstances the brightness of lamps in all 
downward directions should he reduced. In some cases howl¬ 
frosting the lamps may suffice, whereas in other instances the 
use of bowl-enameled lamps, metal caps, dense enclosing glass 
globes, mercury-vapor lamps, or indirect lighting may be 
needed in order to produce satisfactory results. (See discus¬ 
sion of types of lighting units page 23.) 



Fig. 23—Illustrating the shading of local lamps as required by Or¬ 
der 2114. 



Fig. 24—Illustrating the ill-effects of exposed local lamps in one 
case, and the advantages of shading lamps in the other. 

Shading of Lamps for Local Lighting. Order 2114 forbids 
the use of exposed local lamps. Such lamps must be equipped 
with opaque reflectors or translucent reflectors, shades or 
globes which limit the brightness as specified in the order 
(three candle-power per square inch). Metal reflectors are 
preferable, since they are not subject to breakage. 






















42 


INDUSTRIAL. COMMISSION OF WISCONSIN 


The requirements of this order may best be illustrated by 
Figs. 23 and 24. The bare local lamp to the left of Fig. 23 is a 
constant source of glare, which is very injurious to the work¬ 
man’s eye, and is prohibited by the order. To the right, the 
lamp is equipped with a suitable reflector and the provisions 
of the order are complied with. To the right, in Fig. 24, the 
man is working at a lathe illuminated by an exposed lamp. 
More light shines in his eyes directly, than on the work, mak¬ 
ing seeing very difficult and causing ocular discomfort. To 
the left, the same work is done with a well-shaded lamp, as re- r 
quired by the orders. Now a much more powerful light is 
directed to the work and no light from the lamp enters the 
eye directly, greatly increasing the comfort of the man and 
improving vision. 

While this order requires the use of reflectors or shades with 
local lamps, this again is to the advantage of the employer, 
from the economy standpoint. The reflector intensifies the 
light directed to the work, which means that smaller lamps 
may be used. Not only are the workman’s eyes protected, but 
the stray light, which causes the glare, is caught up by the re¬ 
flector and utilized where wanted, at the work. In Fig. 25 four 
types of metal reflectors for local lighting are shown. The 
angle types should be used for lighting vertical surfaces, but 
should always be fixed and in such position that a direct view 
of the lamp is impossible from any working position in the 
shop. The lighting of horizontal surfaces and many machine 
operations may be accomplished by means of the cone or bowl 
type of reflectors. 

As already pointed out local lamps should not be used except 
where nothing else will serve the purpose. The operations in 
any factory or mill, which cannot be illuminated by means of 
overhead lighting, are few indeed. When it is considered that 
a moderate intensity of illumination from an overhead system 
is required in all factories, it becomes a better plan to intensify 
the overhead lighting so that the illumination received at the 
work corresponds to ordinary practice as given in Order 2112, 
rather than install a system of local lamps. When local light¬ 
ing must be used for a given operation, it should be supple¬ 
mentary to the general illumination. In other words its func¬ 
tions should be merely to intensify the illumination at the 


LIGHTING CODE 


43 


work, or to give light in a particular direction, as may be re¬ 
quired. 

Distribution of Light on the Work. The provisions of Order 
2115 make mandatory a reasonably uniform distribution of 
light on the work, and the application has, been fully discussed 
under spacing and mounting of lamps. 

Emergency Lighting. The spirit of Order 2116 requires 
that the emergency lighting system be kept entirely separate 
and distinct from the general lighting system. The emergency 
lighting system is designed to provide illumination sufficient 
for the employes to get out of the building under any and all 
conditions liable to occur, even when the regular lighting sys¬ 
tem has been rendered useless. Hence it is imperative that the 



Pig 25—Local lighting reflectors which adequately shade the lamps. 
Ordinarily metal reflectors are preferred, because they are non-break- 
able. If glass reflectors are used they must be dense enough to reduce 
the brightness of the brightest square inch of reflector surface, to three 
candle-power, as specified in Order 2114. 








































44 


INDUSTRIAL COMMISSION OF WISCONSIN 



emergency lighting be made as reliable as is hnmanly possible. 
This means that the system should be installed in a first class 
manner and so maintained. To this end the emergency sys¬ 
tem should be frequently inspected and the necessary renewals 
of parts and repairs made. 


Electric Emergency service should, when possible, be taken 
from mains that have no connection with those supplying the 
regular lighting system. In the case of factories supplied with 
central station service, the emergency system should be sup¬ 
plied from mains from a separate station, sub-station or trans¬ 
former; whereas factories supplied with isolated plant service 
should arrange for (1) central station service for the emer¬ 
gency system, (2) service from another isolated plant, (3) 
service from a storage battery, or (4) service from a separate 
generating unit driven by a separate prime mover. 

In the case of factories supplied with electrical energy from 
central stations, it may be impossible to get emergency service 
from a separate main. Under this condition it becomes neces- 


Fig. 26—Example of Proper Yard Lighting. 




LIGHTING CODE 


45 


sary to take the emergency service from the same main as 
the regular lighting system service, but the emergency system 
must be supplied from a separate service cabinet, connected to 
the main service to building ahead of the main service fuses, 
and it is good practice to make the size of this emergency sys¬ 
tem several times heavier than required and fused accordingly, 
so that the emergency system is not likely to be rendered use¬ 
less by the blowing of fuses. 

Gas Lamps provide a very satisfactory means of emergency 
lighting, where gas service is available. 

Switching and Controlling Apparatus. Order 2117, as ex¬ 
plained in the note accompanying it, requires the installation 
of properly labeled (or identified by position) switches or 
control apparatus, which will enable the night watchman or 
other qualified persons, to turn on enough lamps in any part of 
the premises to enable them to see their way around with 
safety, thereby making the use of lanterns and flashlights un¬ 
necessary. These switches, preferably, should be installed at 
the points of entrance to the various sections. Sometimes 
several points of control are desirable. 

Maintenance. Order 2118 requires systematic maintenance 
of the natural and artificial lighting equipment. 

In time factory and mill windows become covered with dirt 
and produce greatly decreased natural light in consequence. 
These losses may easily be great enough to affect the workmen 
seriously, and to necessitate the use of artificial light at times 
when otherwise it would not be required. Regular window 
cleaning should therefore be a part of the routine of every 
factory and mill building or group of buildings. 

Lighting installations are designed to give desirable initial 
illumination intensities at the work, but if the illumination is 
to continue satisfactorily, adequate maintenance must be insti¬ 
tuted. In time lamps, globes, and reflectors become covered 
with dust, the lamp bulbs become black and burn out, re¬ 
flectors are cracked and injured, and the electric wiring may 
become defective. Due to all these causes the illumination m 
the shop deteriorates to the point where complaints may come 
in from employes. The losses of time from such circum¬ 
stances, when added up throughout the year are more than 
likely to exceed the expense of systematic attention to such 
items in advance. 


46 


INDUSTRIAL COMMISSION OF WISCONSIN 


How to Make Lighting Measurements. 

Since the intensities of illumination required by the code 
are specified in foot-candles at the work, an instrument must 
be available for measuring intensity of illumination at any 
point desired. The foot-candle meter, Figs. 27 and 28, is a 
compact, completely self-contained and inexpensive instrument 
and designed especially for this, purpose. It weighs about 
three pounds and measures 7% x 6 x 1% inches. The various 
parts are shown in Fig. 28. Once calibrated, the instrument 
may be used over long periods without further attention ex¬ 
cept for occasional renewal of the standard dry cell. 

To make a foot^candle measurement, the voltmeter is set at 
the designated line by adjusting the rheostat, which is in series 
with the dry cell and standard lamp in the light box. Then 
note the point at which the brightness of the translucent spots, 
lighted by the standard lamp inside the light box, equals that 
of the illuminated background, which receives the intensity it 
is desired to measure. In Fig. 29 the foot-candle meter screen 
is shown as it appears under a given intensity of illumination. 
The spots near the right end of the screen are brighter than 
the background; those at the left are darker than the back¬ 
ground. However, somewhere between there is a changing 
point, from bright to dark, at which the brightness of the spots 
is the same as the brightness of the background. In the case 
illustrated, this point is at 5.5 foot-candles. 

Since it is not necessary to manipulate any parts of the in¬ 
strument, where the volt-meter has once been properly set, it 
is possible to walk about rapidly noting the manner in which 
the intensity of illumination changes at the various working 
positions. No knowledge of the principles involved in the foot- 
candle meter are necessary in order to operate it successfully. 
Anyone can be taught to make accurate readings with this in¬ 
strument in ten minutes of instruction. 

Every electrical contractor should have such an instrument 
and every electrical department of industrial plants should be. 
possessed of one. This instrument is as essential to the man 
engaged in the design, installation and maintenance of lighting 
as the voltmeter is to the successful operation of an electric 
power station. Without a foot-candle meter, we are doing 
guess work; with it we can determine quantitatively the light¬ 
ing conditions in a room. 


LIGHTING CODE 


47 



Fig. 27—Foot-Candle Meter. 




Fig. 29—Foot-Candle Meter Screen Indicating 5.5 Foot-Candles. 



















48 


INDUSTRIAL COMMISSION OF WISCONSIN 


The candle-power of the brightest square inch of light source 
as specified in Orders 2113 and 2114 of the code may be meas¬ 
ured by means of the foot-candle meter." An opaque board, 
with a square or circular hole one square inch in area, is 
placed against the surface of the light source in such position 
that the brightest spot emits light through the hole in the 
board. The board must be of such size as to prevent any 
other light from the source to strike the foot-candle meter. 
The foot-candle meter is then placed at some convenient dis¬ 
tance from the unit and read, care being exercised to exclude 
all light from the instrument except that emitted from the 
hole. If the instrument is read at a position one foot distant 
from the light source, the foot-candles observed will also be 
the candle-power; if the photometer is two feet distant, the 
foot-candles observed must be multiplied by four to obtain the 
candle-power; if three feet, they must be multiplied by nine, 
etc., in accordance with the law of inverse squares. 

Light Distribution Curves. 

For the use of illuminating engineers who desire to know 
the exact performance of the five distinct types of reflectors 
(Figs. 5, 7, 8, 10, 11 and 12) previously described, light dis¬ 
tribution curves are given herewith. These curves show the 
candlepower at the various angles and the appended tables 
give the lumens delivered in the important zones. 



LIGHTING CODE 


49 



Porcelain-Enameled 
RLM Dome 



Clear Lamp 


Zone 

Lumens 

% Total 
Clear Lamp 

0 - 60 ° 

1695 

58 

0 - 90 ° 

2220 

76 



Porcelain-Enameled 
RLM Dome 

Bowl Frosted Lamp 




% Total 

Zone 

Lumens 

Clear Lamp 

0 - 60 ° 

1695 

58 

0 - 90 ° 

2130 

73 



Porcelain-Enameled 
RLM Dome 

A 


Opal Cap 


>Total 


Zone 

Lumens 

Clear Lamp 

0 - 60 ° 

1548 

53 

0 - 90 ° 

1928 

66 


Fig. 30—Light Distribution Curve of R. L. M. Standard Dome. (See Fig. 5.) 


























































50 


INDUSTRIAL COMMISSION OF WISCONSIN 



Porcelain-Enameled Bowl 



Clear Lamp 




% Total 

Zone 

Lumens 

Clear Lamp 

0°-60° 

1605 

55 

0 o -90* 

1900 

65 



Porcelain-Enameled Bowl 



Bowl Frosted Lamp 




% Total 

Zone 

Lumens 

Clear Lamp 

0-60° 

1490 

51 

0°-90° 

1750 

60 



Metal-Cap Diffuser 



Silver Cap 




% Total 

Zone 

Lumens 

Clear Lamp 

0-60^ 

1285 

44 

0 90° 

1605 

55 


Fig. 31—Light Distribution Curves of Deep-Bowl Porcelain-Enameled 
and Large Shallow Bowl—Lamp Fitted with Polished Metal Cap (See 
Figs. 7 and 9.) 
































































































LIGHTING CODE 


51 


Mirrored Glass 



Zone 

Lumens 

% Total 
Clear Lamp 

0°~60° 

1750 

60 

0°~90 a 

1985 

68 


Clear Lamp 



Prismatic Industrial 



Clear Lamp 

— 


Zone 

Lumens 

% Total 
Clear Lamp 

0 60 

1840 

63 

0-90° 

2130 

73 

90° 180° 

525 

18 

120-180° 

292 

10 

0°180° 

2660 

91 



Fig. 32—Light Distribution Curves of Mirrored Glass and Prismatic Glass 
Reflectors. (See Figs. 11 and 12.) 










































































■ 












• ■ - •‘•y -- ; 



























